Generally, soil contamination is caused by falling and permeation of contaminants in soil, and with the development of the industry, soil becomes seriously contaminated with hazardous substances like smoke and waste water discharged from plants. Above all, the soil is very seriously contaminated with heavy metals generated around plants. The soil contaminated with arsenic (As) in the heavy metals is mainly found on waste mine or smelter regions, and for example, if the smelter is a contamination cause, the contamination of the soil with arsenic emitted from the chimney of the smelter occurs within a radius of 2 km around the smelter.
In this case, referring to FIG. 1 showing general soil remediation efficiencies in accordance with the particle sizes of soil, soil is separated into coarse soil such as gravel and stone having particle sizes of more than 2 mm, medium soil such as sand having particle sizes between 0.075 mm and 2 mm, and fine soil such as silt and clay having particle sizes of less than 0.075 mm. If the coarse soil, the medium soil and the fine soil are remediated, in view of the remediation cost and time efficiency, the coarse soil is within a substantially economical range, the fine soil is within inefficient economical range, and the medium soil is within intermediate economical range.
Conventional systems for remediating the contaminated soil are configured wherein contaminated soil collected is introduced and remediated into a washing device.
One example of such washing devices is disclosed in Korean Patent Laid-Open Application No. 2003-0005713 (dated on Jan. 23, 2003) wherein the soil washing device includes a pre-washing tank and a main washing tank by which the contaminated soil can be repeatedly washed.
Further, the conventional soil washing device is configured wherein the contaminated soil is collected and poured into a mixing tank for remediation.
However, disadvantageously, the conventional soil washing device just performs the remediation of all of the contaminated soil, irrespective of soil properties and the soil contamination degrees caused by the soil properties, that is, irrespective of the differences of the particle sizes of soil on a paddy field, farm, seaside and mountain range and the contamination degrees of the soil by particle size, thereby showing low efficiencies in remediation work.